Non-invasive monitoring by means of eDNA of pelagic fish in the North Sea and elasmobranchs on the Saba bank

Recent developments allow sustainable monitoring of marine fish via analyses of environmental DNA (eDNA) in seawater. This non-invasive sustainable method targets DNA traces that are shed in the water by all fish species (small and large, demersal and pelagic, free swimming and hiding in rocks). The technique has now been used successfully a handful of times, in Denmark and the USA. The NICO-cruise (National Initiative Changing Oceans by NIOZ) provides a unique opportunity for using eDNA in Dutch waters to determine the community composition of marine bony fish and elasmobranchs (sharks and rays) in the North Sea and on the Saba bank.

Because changes in fish communities are expected due to climate change and ocean acidification eDNA surveys now can provide important reference data for the future. For the North Sea and Saba Bank our aim is to determine the relative abundance of small pelagic fish species. In the North sea the focus will be on very small and young fish (herring, sprat, sandeel) in the coastal zone, because this group is difficult to quantify with conventional methods but extremely important in the pelagic food web as food for predatory fish, seabirds and cetaceans.

On Saba Bank, the focus will be put on small pelagic fish in general (not only the near coastal zone). Currently small pelagics in the Caribbean are almost completely disregarded by fishery surveys and are missing from statistics, whereas local stocks are fished heavily for human consumption (Couperus et al. 2015). In addition, on the Saba bank we will put particular focus on large predatory fish and elasmobranchs (sharks and rays) because these are considered indicators of pristine reef ecosystems.

Methods using eDNA are also applicable to species that hide in rocks, artificial constructions or coral framework and can detect very rare species that go unnoticed in regular monitoring. Therefore we expect that we can add new species to our current list.